1. Field of the Invention
The present invention relates to a transmission adapted for a working vehicle, which is equipped with an engine (referred to as a “horizontal engine”) having a horizontal output shaft, a pair of transaxles for driving respective right and left drive wheels, and a working device.
2. Related Art
There is a well-known conventional vehicle, referred to as a “zero-turn vehicle”, which is equipped with right and left transaxles carrying respective right and left axles so as to individually drive the respective axles. US 2003/0188909 A discloses a mower tractor (riding lawn mower) as one of such zero-turn vehicles. This mower tractor is equipped with an engine having a horizontal engine output shaft, and a transmission continuing to the engine. This transmission has a horizontal input shaft connected to the engine output shaft, and has a PTO shaft for driving a mower unit serving as the working device. The PTO shaft is extended coaxially to the input shaft and horizontally in correspondence to a horizontal input shaft of the mower unit. The input shaft of the transmission projects outward from an outside end of a casing of the transmission toward the engine, while the PTO shaft projects outward from another outside end of the casing opposite the engine.
The right and left transaxles include respective hydraulic motors for driving the respective axles. A pair of hydraulic pumps are disposed in the casing of the transmission so as to supply hydraulic fluid to the respective hydraulic motors of the right and left transaxles. The supply of hydraulic fluid from the respective hydraulic pumps to the respective hydraulic motors depends on pipes. A gear train for driving these hydraulic pumps is disposed in the casing of the transmission so as to transmit power from the input shaft to pump shafts of the hydraulic pumps. Also, in the casing, a clutch for the PTO shaft is interposed between a final gear of the gear train and the PTO shaft, and a brake for preventing inertial rotation of the PTO shaft is provided interlockingly with the clutch.
A vehicle such as disclosed by US 2003/0188909 A tends to have a large transmission because of the above-mentioned arrangement of the two hydraulic pumps. If a vehicle has a narrowed space close to the engine, it is hard to arrange this type of transmission in the space. Further, pipes are needed to fluidly connect the hydraulic pumps of the transmission to the hydraulic motors of the transaxles. Piping of the pipes needs labor and space.
Then, distribution of the hydraulic pumps such that each of the transaxles includes the hydraulic pump together with the hydraulic motor is suggested. This distribution of the hydraulic pumps between the transaxles will make the pipes unnecessary and will make the transmission compact. In the case where each of the right and left transaxles includes the respective hydraulic pump and motor, the transmission has to be reconfigured suitably to drive the transaxles.